Numerous methods and materials exist for the construction of retaining walls. Such methods include the use of natural stone, pored in place concrete, masonry, and landscape timbers or railroad ties. In recent years, segmental concrete retaining wall units which are dry stacked (i.e., built without the use of mortar, have become a widely accepted product for the construction of retaining walls. Such products have gained popularity because they are mass produced, and thus relatively inexpensive. They are structurally sound, easy and relatively inexpensive to install, and couple the durability of concrete with the attractiveness of various architectural finishes.
When constructing a retaining wall it is desirable to utilize some form of connection system between the blocks for the purpose of stabilizing and aligning the wall. For example, the retaining wall system described in U.S. Pat. No. RE 34,314 includes a block design that incorporates, among other elements, a system of pins that interlock and align the retaining wall units, allowing structural strength and relatively quick installation. The system may be adapted for the construction of large walls by employing geogrids which can be hooked over the pins. Such a system is described in U.S. Pat. No. 4,914,876 (Forsberg).
Other connection systems make use of the shape of the block itself for interlock and connection. For example, numerous block designs have used a sheer connector embodied in the blocks shape to align the blocks with a setback, or batter. A common form of such sheer connectors is a rear, downwardly projecting lip or flange. In forming a multi course wall, the blocks are placed such that the flanges contact the upper back edge of the blocks located in the course below. As such, blocks having flanges are caused to become aligned with the blocks positioned below, while at the same time providing a degree of resistance against displacement of individual blocks by earth pressures. In walls formed using blocks of this type, the rear flanges of the blocks create a setback between block courses and cause the wall to slope backward at an angle which is predetermined by the width of the flanges.
Retaining walls using blocks having a rear flange are well known in the art. For example, U.S. Pat. No. 2,313,363 (Schmitt) describes an early use of a retaining wall block with a rear flange. More recently, U.S. Pat. No. 5,294,216 (Sievert) describes a geogrid reinforced retaining wall constructed with retaining wall blocks having rear flanges. Such blocks function adequately for small walls where soil reinforcement is not necessary because they are relatively simple to install and require no special pieces for capping the top course of the wall.
One disadvantage of using blocks having a rear flange is that their use naturally creates a setback between courses which produces a visible line or seam between courses which is noticeable to an observer. In other words, the visual appearance of the wall is such that an observer tends to notice not only the vertical lines between blocks in a course but also the lines at the top and bottom of blocks in each course. Thus, each block in the wall is identifiable as a separate unit from the adjacent blocks. In certain circumstances this may create the desired aesthetic affect. However, in other situations it is desirable to create a more random visual appearance where each block is not separately identifiable.
Retaining walls using blocks having a continuous front flange which extend the entire width of the block are also well known in the art. For Example, U.S. Pat. No. 5,484,236 (Gravier) describes a block with a continuous front flange or lip located at the top of the block and a lateral front notch located at the bottom of the block. The notch is located along the bottom of the front face of the block and is designed to receive the lip of an adjacent block in a lower course of the retaining wall. As with rear flanged blocks, there are disadvantages of prior art continuous front flanged blocks. First, their use naturally creates a set back that accentuates the horizontal lines between succeeding courses of the retaining wall. Second, the continuous flange on these blocks makes it difficult to form smooth inside or outside curves in a wall formed from the blocks. Third, because the flange of a front (or rear) flanged block extends in a straight line across the entire width of the block, the blocks tend to set back excessively when a curve in the wall is constructed.
Thus, a need exists in the art for a retaining wall block and block system which can be used to construct a retaining wall having a connection system which provides for the necessary safety and stability of the wall yet also creates a random or variable visual appearance for the face of the wall and eases the construction of curves by maintaining a desired amount of setback when a curve is constructed.